The southeastern extension of the Tibetan Plateau (SETP) is distributed by the typical longitudinal mountains and has unique climate characteristics and significant regional differences. The diurnal cycles of rainfall amount, frequency, and intensity over the SETP in the warm seasons (May–September) were investigated using high-density hourly station rainfall data and the possible mechanisms were discussed by analysing the ERA5 reanalysis and satellite data. The largest amounts of rainfall appeared on the southern and western margins of the SETP, and the rainfall amount was relatively small at the higher elevations of the SETP. Located at the southern margins of the SETP, the adjacent western (Reg_W) and eastern (Reg_E) regions presented a similar rainfall amount, frequency, and intensity, but the diurnal features of the two regions were quite different. The rainfall amount, frequency, and intensity had dominant peaks in the late afternoon in Reg_W, while in the early morning in Reg_E. A secondary peak in the early morning can be found in Reg_W. The diurnal features of the two regions were closely related with the low-level atmospheric conditions and the distribution of clouds. The enhanced convergence of the anomalous southerly winds and sufficient water vapour after midnight contributed to the nocturnal rainfall at the southern edge of the SETP. In the afternoon, the lower surface air temperature and more stable stratification in Reg_E, as compared with Reg_W, were relatively unfavourable for the occurrence of afternoon convection.

中文翻译：

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青藏高原东南延段每小时降雨特征的区域差异

青藏高原东南延展部（SETP）由典型的纵向山脉分布，具有独特的气候特征和显着的区域差异。利用高密度小时台站降雨数据研究了暖季（5-9月）SETP降雨量、频率和强度的日循环，并通过分析ERA5再分析和卫星数据讨论了可能的机制。降水量最大的出现在东南西北边缘，而在东南西北边缘，降雨量相对较小。位于 SETP 南缘，相邻的西部（Reg_W）和东部（Reg_E）地区呈现出相似的降雨量、频率和强度，但这两个地区的昼夜特征却大不相同。Reg_W的降雨量、频率和强度在下午晚些时候具有主导峰值，而Reg_E在清晨。在 Reg_W 中可以找到清晨的次峰。这两个地区的昼夜特征与低层大气条件和云层分布密切相关。午夜后异常偏南风和充足水汽的增强汇聚促成了SETP南部边缘的夜间降雨。下午，Reg_E较Reg_W较低的地表气温和较稳定的分层，对下午对流的发生相对不利。Reg_W 的强度和强度在下午晚些时候占主导地位，而 Reg_E 的强度则在清晨。在 Reg_W 中可以找到清晨的次峰。这两个地区的昼夜特征与低层大气条件和云层分布密切相关。午夜后异常偏南风和充足水汽的增强汇聚促成了SETP南部边缘的夜间降雨。下午，Reg_E较Reg_W较低的地表气温和较稳定的分层，对下午对流的发生相对不利。Reg_W 的强度和强度在下午晚些时候占主导地位，而 Reg_E 的强度则在清晨。在 Reg_W 中可以找到清晨的次峰。这两个地区的昼夜特征与低层大气条件和云层分布密切相关。午夜后异常偏南风和充足水汽的增强汇聚促成了SETP南部边缘的夜间降雨。下午，Reg_E较Reg_W较低的地表气温和较稳定的分层，对下午对流的发生相对不利。这两个地区的昼夜特征与低层大气条件和云层分布密切相关。午夜后异常偏南风和充足水汽的增强汇聚促成了SETP南部边缘的夜间降雨。下午，Reg_E较Reg_W较低的地表气温和较稳定的分层，对下午对流的发生相对不利。这两个地区的昼夜特征与低层大气条件和云层分布密切相关。午夜后异常偏南风和充足水汽的增强汇聚促成了SETP南部边缘的夜间降雨。下午，Reg_E较Reg_W较低的地表气温和较稳定的分层，对下午对流的发生相对不利。